[CT and MR imaging of pachygyria and agyria]

The CT and MRI manifestations of pachygyria and agyria are presented with a review of the pathological features of the disorders and an evaluation of the diagnostic value of both imaging modalities. 15 cases were analysed retrospectively; of them, 12 were examined with CT and 3 with MRI. The analyses confirm 7 cases with agyria, 5 with pachygyria of bilateral cerebral hemisphere and 3 with limited pachygyria of unilateral hemisphere. On CT and MRI of the whole lesions, the cortex is thickened and the white matter is reduced in proportion. The surface of the brain remains flat and smooth or shows only a few broad gyri and shallow sulci. The border between gray and white matter is smooth. In 12 patients with agyria and pachygyria of the whole brain, the sylvian fissures are shallow, and insulae are exposed. The middle cerebral arteries course superficially along sylvian grooves close to the inner table of the skull. The cerebral contour is "hourglass" or "figure of eight". Associated brain anomalies include the heterotopia of gray matter in 5 cases, the schizencephaly (type I) in 2 cases and the agenesis of the corpus callosum in one case. In conclusion, the pathological changes of pachygyria and agyria are characteristics. CT and MRI are excellent modalities to evaluate these pathological features.